Problem: Factor completely. $16x^2-49y^2=$
Solution: $16x^2-49y^2 = ({4x})^2-({7y})^2$ Using the difference of squares pattern: $({4x})^2 - ({7y})^2 =({4x}+{7y})({4x}-{7y})$ In conclusion, $16x^2-49y^2=(4x+7y)(4x-7y)$ Remember that you can always check your factorization by expanding it.